1. Field of the Invention
This invention relates generally to the field of wireless communications. More specifically, this invention relates to novel and improved techniques for maintaining packet data connectivity in a wireless communications network.
2. Description of Related Art
Recent innovations in wireless communications and computer-related technologies, as well as the unprecedented growth of Internet subscribers, have paved the way for mobile computing. In fact, the popularity of mobile computing has placed greater demands on the current Internet infrastructure to provide mobile users with more support. A crucial part of meeting these demands and providing users with the necessary support is the use of Code Division Multiple Access (CDMA) technology.
CDMA is a digital radio-frequency (RF) channelization technique. CDMA2000 is a recently promulgated CDMA standard. Release 0 of CDMA2000 is introduced in TIA/EIA/IS2000.1-2, entitled xe2x80x9cINTRODUCTION TO CDMA2000 SPREAD SPECTRUM SYSTEMS, RELEASE 0-ADDENDUM 2,xe2x80x9d published in April 2001 and herein incorporated by reference. Release A of CDMA2000 is introduced in IS-2000-A, entitled xe2x80x9cINTRODUCTION TO CDMA2000 STANDARDS FOR SPREAD SPECTRUM SYSTEMS,xe2x80x9d published in June 2000 and herein incorporated by reference.
In various wireless communications system architectures, a mobile station wirelessly connects to a radio access network (RAN) that services a given area. Each RAN includes a base station controller (BSC), which includes a packet control function (PCF). The PCF acts as an interface to a packet data service node (PDSN), which in turn acts as an interface to IP (Internet Protocol) networks.
When a mobile station roams into an area serviced by a RAN, the PCF or PDSN may change. According to the CDMA2000 specification, upon detecting a change in PCFs, the mobile sends an Enhanced Origination Message (EOM) to the RAN indicating that the mobile requires connectivity with a PDSN associated with the RAN. A change in PDSNs generally requires the mobile to negotiate a PPP (Point-to-Point Protocol) session with the new PDSN and perform mobile IP registration.
More particularly, after establishing and maintaining a PPP session with a first PDSN in a first service area, a mobile station may go dormant to conserve resources. The mobile may then venture into a second service area associated with a second PDSN, negotiate PPP, and register mobile IP. The mobile may again go dormant and, as the mobile travels, it may return back to the first service area, where a PPP instancexe2x80x94a xe2x80x9czombie instancexe2x80x9dxe2x80x94associated with the earlier visit is still operative.
In CDMA2000 Release A systems, a mobile station sends wireless IDs of the previous PCF in the EOM. Such systems can determine whether the mobile emerging from dormancy mode had ventured into another PDSN service area during the period of dormancy. If the new PCF is the same as the previous PCF, then the traffic channel is not brought up. Otherwise, the traffic channel is brought up, PPP resynchronizes, and mobile IP re-registers. However, the EOM in CDMA2000 Release 0 systems does not provide for sending of the wireless IDs of the previous PCF. As such, CDMA2000 Release 0 systems cannot identify and handle zombie PPP instances.
Novel techniques consistent with the principles of the present invention, as embodied and broadly described herein, are presented for maintaining packet data connectivity in a wireless communications network. In one embodiment, a mobile station detects a change from a first packet control function (PCF) to a second PCF. The first PCF is connected to a first packet data service node (PDSN). The second PCF is connected to a second PDSN. The mobile station consults a database configured to map at least one previously visited PCF to a servicing PDSN. Based at least in part on the consultation, the mobile station observes one from among a plurality of predetermined origination patterns, wherein an origination pattern defines origination functions to be performed by the mobile station.